1. Development of an algorithm for phenotypic screening of carbapenemase-producing Enterobacteriaceae in the routine laboratory.
- Author
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Robert, Jérôme, Pantel, Alix, Merens, Audrey, Meiller, Elodie, Lavigne, Jean-Philippe, Nicolas-Chanoine, Marie-Hélène, and ONERBA’s carbapenem resistance study group
- Subjects
ENTEROBACTERIACEAE ,CARBAPENEMASE ,ALGORITHMS ,CARBAPENEMS ,DISC diffusion tests (Microbiology) ,ANTIBIOTICS ,BACTERIAL protein metabolism ,BACTERIAL protein analysis ,BETA lactam antibiotics ,CEPHALOSPORINS ,DRUG resistance in microorganisms ,ENZYME inhibitors ,HYDROLASES ,PENICILLIN ,MICROBIAL sensitivity tests ,TICARCILLIN ,IMIPENEM ,PHARMACODYNAMICS ,PHYSIOLOGY - Abstract
Background: Carbapenemase-producing Enterobacteriaceae (CPE) are difficult to identify among carbapenem non-susceptible Enterobacteriaceae (NSE). We designed phenotypic strategies giving priority to high sensitivity for screening putative CPE before further testing.Methods: Presence of carbapenemase-encoding genes in ertapenem NSE (MIC > 0.5 mg/l) consecutively isolated in 80 French laboratories between November 2011 and April 2012 was determined by the Check-MDR-CT103 array method. Using the Mueller-Hinton (MH) disk diffusion method, clinical diameter breakpoints of carbapenems other than ertapenem, piperazicillin+tazobactam, ticarcillin+clavulanate and cefepime as well as diameter cut-offs for these antibiotics and temocillin were evaluated alone or combined to determine their performances (sensitivity, specificity, positive and negative likelihood ratios) for identifying putative CPE among these ertapenem-NSE isolates. To increase the screening specificity, these antibiotics were also tested on cloxacillin-containing MH when carbapenem NSE isolates belonged to species producing chromosomal cephalosporinase (AmpC) but Escherichia coli.Results: Out of the 349 ertapenem NSE, 52 (14.9%) were CPE, including 39 producing OXA-48 group carbapenemase, eight KPC and five MBL. A screening strategy based on the following diameter cut offs, ticarcillin+clavulanate <15 mm, temocillin <15 mm, meropenem or imipenem <22 mm, and cefepime <26 mm, showed 100% sensitivity and 68.1% specificity with the better likelihood ratios combination. The specificity increased when a diameter cut-off <32 mm for imipenem (76.1%) or meropenem (78.8%) further tested on cloxacillin-containing MH was added to the previous strategy for AmpC-producing isolates.Conclusion: The proposed strategies that allowed for increasing the likelihood of CPE among ertapenem-NSE isolates should be considered as a surrogate for carbapenemase production before further CPE confirmatory testing. [ABSTRACT FROM AUTHOR]- Published
- 2017
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